SX1242 Просмотр технического описания (PDF) - Semtech Corporation

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SX1242

Low Cost Integrated Transmitter IC 344.940 MHz RF Transmitter

Semtech Corporation 

ADVANCED COMMUNICATIONS & SENSING

SX1242

Integrated Transmitter IC

DATASHEET

3. Circuit Description

The SX1242 compromises a low-consumption fractional-N Sigma-Delta type PLL and power amplifier.

A simplified block diagram of the internal architecture and application schematic is illustrated below in Figure 3

GND

1

RFOUT

8

v

v

v

DATA

2

CP

VDD

M/N 7

GND

3

XTAL

4

TX ENABLE

PFD

6

VDD

ΣΔ

5

v

Figure 3. SX1242 Simplified Block Diagram and Application Schematic

3.1. PLL

The VCO operates at twice the RF channel frequency and is derived from a 26 MHz crystal oscillator reference

3.2. Transmitter

The Power Amplifier (PA) is connected to the RFOUT pin and delivers 12 dBm in a 50 ohm load. The bit stream to be

transmitted over the air is sent to the chip via the pin DATA. During modulation, the rising and falling transitions are

smoothed with a ramp-up/ramp-down time of typically 20 μs via the PA reference DAC.

3.3. SX1242 Operating Modes

The SX1242 operating modes are defined by the status of the pin TX ENABLE and are documented in Table 5.

SX1242, Rev 1, November 2010

©2010 Semtech Corp.

Page 7

www.semtech.com

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